【作者】 纪婧；

【导师】 邱江平；

【作者基本信息】 上海交通大学 ， 生态学， 2010， 博士

【摘要】 膜-生物反应器技术（MBR）是一种卓越的水处理与回用技术，与传统活性污泥技术相比，膜-生物反应器具有很多优势。然而，由膜污染导致的高昂维护费用和操作不便是制约MBR广泛应用的主要瓶颈，研究膜污染过程和机理对于控制膜污染、降低MBR运行成本具有重要意义。近年来，通过向膜-生物反应器中投加过滤助剂/抗污染剂，人为的改善反应器中活性污泥混合液的性质，从而减缓膜污染进程成为一种新兴的膜污染控制技术。本研究选取了六种最常使用的絮凝剂：水和硫酸铝（Al₂（SO₄）₃.xH₂O）、聚合氯化铝（PAC）、三氯化铁（FeCl₃）、聚合硫酸铁（PFS）、壳聚糖（Chitosan）和聚丙烯酰胺（PAM），对其作为膜污染控制剂的作用和机理分别做了深入的探讨。根据其化学性质，六种絮凝剂分别属于单体金属盐，聚合金属盐和有机高分子絮凝剂三类。实验结果表明，所有絮凝剂都对改善膜-生物反应器活性污泥混合液的可过滤性起到了显著的作用。在操作通量为20L/m2.h时，各MBR中的膜污染速率排序为PFS反应器＜壳聚糖反应器＜聚丙烯酰胺反应器＜三氯化铁反应器＜聚合氯化铝反应器＜水合硫酸铁反应器。其中，添加壳聚糖和PFS可以使MBR可持续操作时间延长至对照反应器的约7倍。在膜污染进程中透膜压力（TMP）的上升分三个阶段：第一阶段发生在初始的几小时内，由于膜孔的缩窄或堵塞造成的膜表面特性的改变，导致透膜压力突然的上升。第二阶段表现为透膜压力的长时间慢速上升过程，主要原因是膜表面的凝胶层累积。凝胶层的主要来源是膜对混合液中大分子物质的截留。第三阶段是TMP的突然跃升并导致膜过滤无法继续操作，主要特点是泥饼层的堆积和TMP增长的“自我加速”。在这三个阶段中，对膜污染速率起到关键性作用的污染物是不同的，而各种絮凝剂作用于每个阶段的效果和机理也各有区别。本研究将污染物分为溶液相和固体相两个部分，就各种絮凝剂对污染三阶段的作用分别作了细化和深入的探讨。对于溶液相污染物而言，为了进一步细化不同性质以及不同颗粒大小的污染物的污染趋势以及絮凝剂对每一种污染物组分和性质的调节作用，本研究利用凝胶渗透色谱（GPC）对污染物的颗粒大小以膜孔径为标准进行了细分，明确了目标污染物的分子量范围。在此基础上进一步利用傅立叶红外转换光谱（FTIR）对污染物的物质属性进行了辨别，找出了易造成膜内部污染的物质的化学成分。结果表明，分子量大于100KDa的可溶性物质才是需重点控制的污染物，而蛋白质和多糖类物质是膜内污染的主要贡献者。多种絮凝剂均能有效地降低膜孔中蛋白和多糖含量，减轻膜的不可逆污染；降低液体相大分子浓度，减缓凝胶层的形成速率和膜总孔隙率的衰减速率。对于固体污染物，即活性污泥颗粒而言，本研究分别探讨了活性污泥絮体的（1）形态学指标：絮体平均粒径（dp）和絮体分型维数（df）；（2）理化指标：污泥絮体表面电荷（本研究中以污泥表面Zeta电位表征），絮体表面相对疏水性（RH），活性污泥混合液动力学粘度（η）（3）污泥絮体的生化成分：EPS的浓度。考察了各种絮凝剂在不同剂量下对各个指标的改变作用以及对膜污染带来的影响。在絮凝剂-MBR这个二级多因素系统中。膜污染的影响因子众多，机理复杂。为了将量纲不同的各影响因子进行统计分析，本研究采用了归一化，标准化的方法对数据进行了处理，并进一步采用线性回归和多元直线回归等统计方法对添加絮凝剂的MBR中，在5个剂量梯度下的所有指标的数据进行了分析整合，得到了各絮凝剂的膜污染控制关键因素以及各因素的膜污染贡献率。结果表明，絮凝剂按其对不同指标的作用因子可以分为有机和无机两大类。有机絮凝剂对于改变污泥形态学性质的作用较大，壳聚糖和聚丙烯酰胺的膜污染控制效果是通过降低和转化溶液相中的大分子物质，增大污泥的平均粒径和增加污泥絮体的疏松度而实现的。无机絮凝剂对絮体的理化性质作用显著但对于污泥的形态结构以及混合液的粘度的作用可忽略。无机絮凝剂膜污染控制效果是通过降低SMP浓度，中和污泥絮体表面电荷，即增加絮体Zeta电位和增加污泥絮体表面疏水性实现的。用选定的关键因子对每一絮凝剂进行了膜污染速率与关键因子的经验公式拟和，结果是所有公式与实验实测数据的拟和效果非常好。更多还原

【Abstract】 Membrane bioreactor has been regarded as one of the most promisingtechnologies for wastewater treatment and reclamation due to manyoutstanding advantages over conventional activated sludge processes.However, membrane fouling has still been a major barrier limiting its wideapplication because fouling could cause high operating costs andinconvenience in application .Recently, application of filter aids or antifoulingagents in MBR to modify biomass characteristics artificially for alleviation ofmembrane fouling has been considered as a new technology of fouling control.this study, the effects of addition of six types of flocculants （aluminiumsulphate, ferric chloride, polyaluminium chloride, polymeric ferric sulfate,Chitosan, polyacrylamide） on mitigation of membrane fouling in membranebioreactors （MBR） were investigated respectively. According to actionmechanism, the flocculants adopted could be classified as monomer, inorganicpolymer and high molecular weight organic flocculants respectively. In membrane fouling process，the rise in TMP is described as a 3-stageprocess. The first stage occurs in a period of afew hours and involves abruptTMP rise due to“conditioning”presumably by pore blockage and closure.Stage 2 is a prolonged period of slow TMP rise，which is ascribed to formationof gel layer. Stage 3 is a sudden rise in TMP due to accumulation of cake layer.The effect of flocculants on membrane pore blocking, gel layer and cake layerresistance were analyzed respectively.Significant improvement of the sustainable filtration was demonstrated in allflocculants added MBRs. The membrane fouling rate of the MBRs operatedunder 20L/m2.h flux was in the order of Control MBR （no filter aid added）<Al₂（SO₄）3 <PAC < FeCl₃< PAM < Chitosan < PFS added MBR. For theChitosan and PFS added MBRs, the sustainable filtration time at optimumdosage were nearly 7 times more than that in the control MBR. Membraneinner fouling due to pore blocking was analyzed by means ofFourier-transform infrared microscope （FTIR）. Compared to the control MBR,significantly low protein and carbohydrate concentrations were measured inthe membranes of the flocculants added MBRs, indicating that flocculantscould effectively alleviate membrane pore blocking. Gel PermeationChromatography （GPC） analysis suggested that both the concentration andmolecular weight distribution of the macromolecules in supernatant play animportant role in gel layer formation and loss of membrane porosity. Thereduction of fouling rate in the filter aids added MBRs could be attributed to lower concentration and reduction in molecular weight of macromolecules insupernatant.The biomasses in various MBRs were characterized by morphologicalproperties （mean floc size （dp）, fractal dimension （df））, physical parameters（surface charge, relative hydrophobicity （RH）, dynamic viscosity） and thebiochemical components of the mixed liquor （concentration of extracellularpolymeric substances （EPS））. Statistical methods such as normalization,nondimensionalization and multiple linear regressions were used to identifythe dominant membrane fouling contributors and to simulate membranefouling rates. The results demonstrated that the key factors affectingmembrane fouling varied in different flocculants added MBRs. Organicpolymeric flocculants have significant effects on biomass morphologicalproperties. Membrane-fouling alleviation was mainly due to the decrease inSMP and df as well as the increase in dp. Inorganic flocculants have strongeffects on SMP, EPS, Zeta potential and RH but weak effects on d p, df andviscosity. For the inorganic flocculants added MBRs, the lower fouling ratecould be mainly attributed to the decrease in SMP and surface charge as wellas the increase in RH. For each type of flocculants, the empirical equations ofsustainable filtration time （Γ45） were simulated to predict membrane foulingrates in different MBRs.更多还原